1. Field of the Invention
This invention pertains generally to the field of cockpit indicators or display units that provide flight information to the pilot or flight crew of an aircraft, and more particularly to highway in the sky (“HITS”) pathway depictions on one or more display units providing an artificial horizon through a synthetic vision system (“SVS”), an enhanced vision system (“EVS”), a combined SVS-EVS vision system, and/or a vision system that may produce a classic electronic primary flight display (“PFD”).
2. Description of the Related Art
Cockpit indicators may provide navigation and/or course information to a pilot which allows the pilot to determine if the aircraft is flying on course with a flight plan. Traditional or classic indicators have been driven using signals generated using ground-based navigation aids that are received by the aircraft. Data represented in the signals is used to provide course information to the pilot by depicting or providing vertical and/or horizontal bars (i.e., “needles”) where the pilot is required to “fly the needles” to stay on course. If the aircraft was on course, the needles would be centered on the indicator.
With the existence of a satellite-based navigation system such as global positioning system (“GPS”) and with the growing ability to depict the scene outside of the aircraft with a synthetic and/or enhanced image on a tactical display unit such as a PFD, there has been a trend in the aviation community to replace needles with a HITS pathway for providing course information. In one form, a HITS pathway comprises a “tunnel” where the pilot is required to “fly the tunnel” to stay on course.
The depiction of the tunnel is based on, in part, the flight plan between successive navigation fixes (e.g., waypoints) that may or may not have corresponding altitude constraints. A system such as a flight management system (“EMS”) may receive the flight plan and generate flight plan data divided into lateral flight plan and vertical flight plan components from which a HITS pathway is generated.
Although a HITS pathway provides useful information and may improve situational awareness, situational awareness may still be attenuated if a HITS pathway clutters or obscures the presentation of other flight information on an aircraft display unit, especially if a HITS pathway is depicted as a wireframe and the aircraft is “flying the tunnel” and the wireframe HITS pathway symbols converge. Moreover, too much focus of “flying the tunnel” may provide a false sense of security to the pilot; it may lead to a pilot erroneously focusing on “staying in the tunnel” while neglecting other duties.